lot of older bikes had this feature
but i have found you had to run them off a hill and bump start in second gear
had an old one once used a 6volt dry cell battery from big flash light
and a push button put it in to the e/start position
hold button down and when it started let off button so you do not kill the dry cell
if the mz is your get to work daily driver see this site for electrical upgrade
http://www.powerdynamo.biz/deu/systems/lists/mz.phpthis is not cheap but the way to get it to run the best it can
dave